Electroactive materials, a process for their preparation as well as the use thereof

ABSTRACT

Stable, electroactive material which when a potential is applied from the outside is subjected to one or more reversible redox reactions, for use in devices with an electrochromic display or another electrochromic color change or in batteries. 
     The material comprises a condensed ring structure, the oxidized form of which is of the formula ##STR1## in which R 1 , R 2 , X, and A may have any meaning with the proviso that the condensed ring structure maintains the reversible properties. 
     The material can be prepared by various processes and it is suited for use as electrochromic material for use in devices with an electrochromic display or as coating on windows because it presents a distinct and easily visible color change when it is subjected to a potential. In addition, the material is suited for use in rechargeable batteries because is possesses an excellent capacity and reversibility.

This application claims benefit of international applicationPCT/DK94/00225, filed Jun. 9, 1994.

TECHNICAL FIELD

The present invention relates to a stable, electroactive material whichwhen a potential is applied from the outside is subjected to one or morereversible redox reactions, for use in devices with an electrochromicdisplay or another electrochromic colour change or in batteries, and toa process for the preparation of the stable, electroactive material witha single, reversible, redox-active condensed ring structure or in formof an oligomeric or polymeric material containing several suchredox-active condensed ring structures.

The electroactive material according to the invention can be anelectrochromic material of the type changing colour by one or morereversible redox reactions. The invention relates also to the use ofsuch electrochromic materials in devices with an electrochromic displayor as coating on windows.

The invention relates in addition to the use of the stable electroactivematerials in rechargeable batteries.

BACKGROUND ART

Elektrochromism refers to a special property of particular materials,subsequently referred to as electrochromic materials, which in areversible manner can change colour (spectral absorption and/orreflection) as a reaction to a potential applied from the outside.

Electrochromic materials can be widely used as they for instance can beused for electrochromic display for use in light signs or anotherdisplay use where it is possible in no time to change showcards, todisplay "today's special" or the like. Electrochromic materials can alsobe used in form of window coatings allowing a subduing of the sunlightas required. In order to illustrate in greater detail the use ofelectrochromic materials in devices with an electrochromic displayreference can for instance be made to an article by K. Bange and Th.Gambke "Electrochromic Materials for Optical Switching Devices", Adv.Mater. 2 (1990) No. 1, pages 10 to 16, as well as to U.S. Pat. No.4,184,751 (Nicholson).

Numerous inorganic and organic electrochromic materials are known, amongwhich the best tested and most used electrochromic material iswolframtrioxide WO₃ displaying a cathodic coloration. Otherelectrochromic materials based on a cathodic coloration are for instanceMOO₃, V₂ O₅, Nb₂ O₅, and TiO₂. Oxides of irridium, rhodium, nickel, andcobalt displaying an aniodic coloration can also be mentioned. Among theorganic electrochromic materials viologenes can be mentioned, viz.dialkyl derivatives of 4,4'-bipyridinium salts, pyrazoline, pyridine,the tetrathiafulvalene system, and organometallic compounds, such ascomplexes of metal and diphthalocyanine. Polyaniline can furthermore bementioned. The advantages of the organic electrochromic materials aretheir fast conversion capacity and their simple handling in theconstruction of electrochromic devices. An undesired and irreversibleside effect of the weakly bound hydrogen ions and nitrogen ions is,however, one of the commonly known drawbacks of organic electrochromicmaterials as such side effects cause short lives and a poor stability toultraviolet light.

EP Publication No. 32 991 (Engler et al.) discloses an electrochromicmaterial in form of a polymer resin, to which electroactive moleculesare covalently bonded and in which a non-electroactive ionic salt isincorporated. The object of the latter material is to improve theswitching speed and the stability of the electrochromic material. Theseknown materials present, however, still a poor stability. In addition, arather indistinct change of colour appears, which is probably due to thestructure of the materials, said structure not providing sufficienthindrance of interactions between the individual redox active units.

Nomura et al., J. Macromol. Sci.-Chem., A26 (2 & 3), pages 593 to 608(1989) discloses an electrochromic material in form of a polymer complexbetween electrochromic polytetramethylene viologene (PVT) andpoly(p-styrene sulphonic acid) (PSS).

This PTV/PSS polymer complex has, however, a low conductivity and musttherefore be used in combination with a conductive powder as acomposite. The conductive powder is a mixture of TiO₂ and SnO₂ admiredSbO₂. The addition of the conductive powder is, however, disadvantageousin making the electrochromic material opaque, which deteriorates theelectrochromic display and limits the use of the material for reflectivedisplay.

Thus a demand exists for an improved electrochromic material encumberedwith the advantageous capacity of fast colour changes, such as it isknown in connection with conventional organic electrochromic materials,which is easy to handle, and which is encumbered with an improvedstability to light and other physical or chemical effects.

A demand also exists for a stable electroactive material, which, when anexternal potential is applied, is subjected to a reversible redoxreaction in such a manner that the material is suited for use inrechargeable batteries.

BRIEF DESCRIPTION OF THE INVENTION

The above demands are met by a stable, electroactive material, whichwhen a potential is applied from the outside is subjected to one or morereversible redox reactions, for use in devices with an electrochromicdisplay or another electrochromic colour change or in batteries, saidmaterial being characterised by containing at least one condensed ringstructure I of one of the formulas I red or I ox in the redox reactionequation: ##STR2## in which the groups X, which may be identical ordifferent, are O, S or NR₃,

where the structures A, which may be identical or different, may be anymolecular structure not blocking the redox reaction, and, if desired,may carry one or more identical or different substituents R₄,

where R₁, R₂, R₃, and R₄, which may be identical or different, may beany substituent not blocking the redox reaction, and where one or moreof the substituents R₁, R₂, R₃, and R₄ may also form part of a linkerresidue L, which is attached to one or more additional ring structuresI, and

where L is a divalent or polyvalent group not blocking the redoxreaction.

The electroactive material according to the invention is remarkable forpossessing a high chemical stability which also involves a highphotochemical stability. The material can in a simple manner be modifiedsuch that it for instances can form part of a polymer, and accordinglythe material can be dissolved in organic solvents and shaped byconventional dipping and printing techniques. The material according tothe invention deviates in this respect from electrochromic materialsbased on inorganic electrochromic materials, and from most organicelectrochromic materials, such as phthalocyanines, which can only beapplied in form of coatings by methods involving a high vacuum and/orhigh temperatures.

The electroactive materials according to the invention areadvantageously prepared in form of an oligomer or polymer by simplepolymerisation processes, either before or during the coating process,which allows a high design freedom concerning the preparation of thefinal electroactive laminate for use in conventional devices, such asdevices for electrochromic display or as window coatings.

A further advantage of the electroactive materials according to theinvention is that both the oxidized molecular structure of the formula Iox and the reduced (coloured) structure of the formula I red includefilled electron band structures. The resulting stability is very highcompared to other electrochromic systems where the coloured state ischaracterised by being a radical, i.e. a structure with a singleunpaired electron in the outer electron band structure. As it is known,radicals are very reactive compounds with a tendency to react with othersubstances, such as present oxygen or water, which results in anirreversible decomposition. This drawback is for instance found inviologen-based dyes.

The material is conductive per se to a certain extent, and accordinglyit is not necessary to add a conductive powder as suggested in thepreviously mentioned article by Nomura et al. in order to ensure thenecessary conductivity. The stable electroactive material according tothe invention presents typically a specific resistance lower than 10⁹ohm·cm.

The high stability of the material according to the invention renders itsuited for use also in rechargeable batteries, because in such batteriesit is possible to obtain a significant accumulation of the charge inlayers of material produced from the electroactive material according tothe invention.

The scope of the applicability of the invention appears from thefollowing detailed explanation. It should, however, be underlined thatthe detailed explanation and the specific Examples merely illustratepreferred embodiments of the invention, as various alterations andmodifications can be carried out within the scope of the invention andare obvious to persons skilled in the art in view of the detailedexplanation.

DETAILED DESCRIPTION OF THE INVENTION

The molecular structures A can in principle be any molecular structuremeeting the decisive condition that they have no blocking effect on thereversible redox reaction.

Typical molecular structures A are ring structures condensed with ring 1and ring 3, respectively, in the ring structure of the general formulaI.

Thus A can typically consist of or comprise a 5 or 6-linked ringstructure optionally containing one or more, especially one or twohetero atoms selected among N, O, and S, preferably such being of anaromatic structure.

Examples of such ring structures are benzene, thiophene, pyrrole, furan,thiazole, pyridine, pyrimidine, imidazole, pyrazole, pyradazine, andpyrazine.

Further examples of ring structures A are ring structures of the abovetype which are condensed with one or more additional rings, especially 5or 6-linked rings selectable among both carbocyclic and heterocyclicrings, and which can also be aromatic, whereby, however, the aromaticcharacter is usually of a minor importance for the rings not directlycondensed with ring 1 or ring 3.

Examples of ring structures A including at least one ring beyond the onecondensed with ring 1 or ring 3 are naphthalene, anthracene,phenanthrene, indole, isoindole, indanzole, isoquinoline, quinoline,quinazoline, quinoxaline, phthalazine, phtheridine, benzofuran, andisobenzofuran.

Ring structures A can be unsubstituted or they can be substituted withone or more, for instance from 1 to 6, such as 1 to 4 substituents, R₄,which can be identical or different. Such substituents are again subjectto the criteria that they must not block the reversible redox reaction.

Both the substituents R₄ and the substituents R₁, R₂, and R₃ are subjectonly to the criteria that they must not block the reversible redoxreaction.

The substituents R₁, R₂, R₃, and R₄ can advantageously be utilized foradapting the properties of the molecular structure of formula I, such asfor adapting the solubility especially in organic solvents, such astetrahydrofuran, chloroform or toluene, in such a manner that thematerial is easily applied onto a carrier material.

Examples of substituents R₁, R₂, R₃, and R₄ ensuring the desiredsolubility are straight chained and branched chains with 1 to 24 chainatoms selected among C, O, N, S, and Si, such as alkyl with 1 to 18carbon atoms, thioalkyl with 1 to 18 carbon atoms and 1 to 6 sulphuratoms, oxoalkyl with 1 to 18 carbon atoms and 1 to 6 oxygen atoms, aswell as alkenyl with 1 to 18 carbon atoms, and these groups can, ifdesired, contain inactive or reactive substituents. Chain groups withcarboxyl groups or carboxyl derivative groups can for instance be used,where these groups can be utilized in connection with incorporation ofthe molecular structure I in a polymeric material.

The substituents R₁, R₂, R₃, and R₄ can also be selected in order tochange the electrochemical properties. Thus it is possible by means ofeither electronegative substituents, such as halogen, nitro or cyano, orelectropositive substituents, such as hydroxy, alkoxy or alkylamino, tomove the absorption spectra towards lower or higher wavelengths,respectively.

According to a particularly attractive embodiment, the individualelectroactive units are bonded together in chains by means of linkerunits with the effect that oligomeric or polymeric structures areformed. The use of flexible linker units results in good propertiesfacilitating the producing processes in which the stable, electroactivematerials according to the invention are used, and good film-formingproperties are obtained. Correspondingly, a polymeric structure rendersit possible to obtain an improved stability of the final product becausethe electroactive part of the molecular structure is locked in astructure and cannot therefore diffuse into other layers of a laminateincluding the material. In this manner it is avoided that theelectrochemical efficiency of the product is reduced.

As the molecular structure of the general formula I thus can form partof oligomeric or polymeric structures or molecules, it should beunderstood that the above examples of meanings of the ring structures Aand the substituents R₁, R₂, R₃, and R₄ for practical reasons cannot becomplete in the present specification and cover all the numerouspossibilities within the scope of the present invention. Here, thecriteria must, of course, again be that the reversible redox reactionmust not be blocked, but may be supported or modified so as to adapt thestable readox-active material to the particular application in question.

The only criteria for the linker units L is that they should not blockthe reversible redox reaction. Typically, L can be a straight chained orbranched, divalent or polyvalent group with 3 to 150, preferably 5 to 20chain atoms selected amont C, O, N, S, Si.

Typically, such linker units L are pure carbon chains or polyetherchains of the formula ##STR3## where (x+1)·m+y=3-150, or silicones forinstance of the formula ##STR4## where m₁ is 2 to 75 and R is hydrogenor an organic group.

In electroactive materials according to the invention, the linkerresidues L are typically of a chain length of from 0.4 to 20 nm.

The use of the stable electroactive materials in dissolved form, forinstance for forming coatings, renders it possible to typically usesolvents relatively inpolar relative to water, such as halogenatedand/or aromatic hydrocarbons.

Examples of electroactive materials according to the invention appearfrom Tables 1 and 2.

                                      TABLE 1                                     __________________________________________________________________________    Example of Compounds of formula I                                              ##STR5##                                                                     Intern.                                                                       code                                                                              X (1)                                                                              R.sub.3 (1)                                                                            X (3)                                                                              R.sub.3 (3)                                                                            R.sub.1                                                                            R.sub.2                                                                         R.sub.4                                __________________________________________________________________________    MJ 42                                                                             N-R.sub.3                                                                          cyclohexyl                                                                             N-R.sub.3                                                                          cyclohexyl                                                                             H    H --                                     MJ 45                                                                             N-R.sub.3                                                                          butyl    N-R.sub.3                                                                          butyl    H    H --                                     MJ 46                                                                             N-R.sub.3                                                                          hexyl    N-R.sub.3                                                                          hexyl    H    H --                                     MJ 30                                                                             N-R.sub.3                                                                          phenyl   N-R.sub.3                                                                          phenyl   H    H --                                     MJ 22                                                                             N-R.sub.3                                                                          (CH.sub.2).sub.2 Otosyl                                                                N-R.sub.3                                                                          (CH.sub.2).sub.2 Otosyl                                                                H    H --                                     __________________________________________________________________________    Intern.                                Position                               code                                                                              X (1)                                                                            R.sub.3 (1)                                                                            X (3)                                                                            R.sub.3 (3)                                                                            R.sub.1                                                                         R.sub.2                                                                         R.sub.4                                                                              for R.sub.4                            __________________________________________________________________________    MJ 24                                                                             N-R.sub.3                                                                        H        N-R.sub.3                                                                        H        H H carboxy                                                                              3                                                                      carboxy                                                                              10                                     MJ 18                                                                             N-R.sub.3                                                                        H        N-R.sub.3                                                                        H        H H hexylamino                                                                           2                                      MJ 19                                                                             N-R.sub.3                                                                        H        N-R.sub.3                                                                        H        H H SO.sub.2 NHbutyl                                                                     2                                      MJ 68                                                                             O  --       O  --       Cl                                                                              Cl                                                                               --                                           MJ 71                                                                             O  --       O  --       Cl                                                                              Cl                                                                              methyl 2                                                                      methyl 9                                      MJ 72                                                                             O  --       O  --       H H methyl 2                                                                      methyl 9                                      MH 73                                                                             O  --       O  --       H H carboxy                                                                              2                                                                      carboxy                                                                              9                                      MJ 84                                                                             N-R.sub.3                                                                        H        N-R.sub.3                                                                        H        H H nitro  3                                                                      nitro  10                                     MJ 2                                                                              N-R.sub.3                                                                        H        N-R.sub.3                                                                        H        H H  --                                           MJ 3                                                                              N-R.sub.3                                                                        H        N-R.sub.3                                                                        H        H H carboxy                                                                              2                                      MJ 6                                                                              N-R.sub.3                                                                        2-propenyl                                                                             N-R.sub.3                                                                        2-propenyl                                                                             H H  --                                           __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    Examples of compounds of formula I                                             ##STR6##                                                                     Internal Code                                                                        X   L                                                                  __________________________________________________________________________    MJ 28  NL  butylene                                                           MJ 90  NL  (CH.sub.2).sub.3 O(CH.sub.2).sub.4 O(CH.sub.2).sub.3               MJ 91  NL  (CH.sub.2).sub.12                                                   MJ 100                                                                              NL  (CH.sub.2).sub.2 O(CH.sub.2).sub.2 O(CH.sub.2).sub.2               MJ 97  NL  (CH.sub.2).sub.2 O(CH.sub.2 ).sub.2 O(CH.sub.2).sub.2 O(CH.sub.               2).sub.2                                                           __________________________________________________________________________

The electroactive molecular structures of the formula I can be preparedin a number of various ways according to the meanings of thesubstituents. Below suitable methods are illustrated.

METHOD A

A particularly suited and novel method for preparing the ring structuresI is the method A indicated in claim 10 a). Method A is in principlesuited for the preparation of any ring structures I. Examples ofcompounds advantageously prepared by method A are ring structures I, inwhich X has the meaning NR₃. This embodiment is illustrated in Example3. The quinone of the formula III is typically a 2,5-dimethoxy-quinoneor a 2,5-dihydroxyquinone, and preferably a 2,5-dimethoxyquinone isused. The reaction usually employs 2 mol amine of formula II per molquinone of the formula III. The reaction is performed under slightlyacid conditions, such as in the presence of a weak organic acid, such asacetic acid, and the reaction mixture is advantageously heated underreflux.

Method A is also suited for the preparation of7,14-dioxa-5,12-di-aza-pentacenes, where the starting material used is2-hydroxyaniline optionally containing one or more R₄ -substituents,said R₄ having the meaning stated in the ring structure I.

METHOD B

A further suited method B for the preparation of a particular group ofring structures Ib being a sub-group of the ring structures I isindicated in claim 10 b). Method B is particularly suited for thepreparation of unsymmetrical tetra-aza-pentacenes, i.e. compounds of theformula Ib, in which A bonded to ring 3 is a benzene ring substitutedwith at least one substituent R₄. Example 5 illustrates the preparationof an unsymmetrical tetra-aza-pentacene.

The condensation of the compounds of the formula IV is performed in thepresence of an oxidation agent, such as FeCl₃ or CeCl₄. The resultingcompound of the formula V is reacted with an equimolar amount of thecompound of the formula VI. This reaction is advantageously performed byusing a high-boiling, organic acid as solvent, such as benzoic acid orp-toluene sulphonic acid.

The stable electroactive material according to claim 1 is often presentin form of an oligomeric or polymeric material containing several ringstructures I linked together by means of linker residues L of themeaning stated in claim 1. Oligomeric or polymeric materials includetypically materials composed of repetition units, where the condensedring structure I forms part of each repetition unit. The number ofrepetition units n is typically in the range of 5 to 1,000, preferablybetween 5 to 500. Such oligomeric or polymeric materials can also beprepared in a number of different ways.

METHOD C

A suited method C for the preparation of a particular group ofpolymerised ring structures Ic being a sub-group of the ring structuresI is described in claim 11 c). This method is described in greaterdetail in the Examples 1 and 6. In the compound used as startingmaterial of the formula VII, the leaving group Q₂ can typically behalogen or a sulphonate group, such as mesylate or tosylate or acorresponding leaving group. The nitro groups of the compound of theformula IX are reduced in a conventional manner, such as by means ofstannous chloride in acid liquid. The polymerisation degree n ispreferably in the range of 5 to 1,000, especially 5 to 500.

METHOD D

Claim 11 d) indicates a suited method D for the preparation of aparticular group of ring structures Id, where the polymerisation isperformed through the A ring structures.

METHOD E

Claim 11 e) indicates a method E for the preparation of a particularoligomeric or polymeric structure Ie being a sub-group of the ringstructures I. By method E, the linking is performed through theX-groups. The reaction is an electrophilic reaction, which, ifnecessary, can be performed in the presence of a base as catalyst, suchas in an aprotic, polar solvent, such as DMF or tetrahydrofuran.Examples of such a base are for instance strong bases, such asbutyllithium, NaH, and potassium-t-butoxide. The leaving group Q₄ inconnection with formula XV can typically be halogen or a sulphonategroup, such as metsylate or tosylate, or a corresponding leaving group.The compound of the formula XIV used as starting material by method Efalls within the definition of the ring structure I, and such startingmaterials can advantageously be prepared by means of the above method A.Method B can also be used for preparing compounds of the formula XIV, inwhich R₃ in ring 3 is hydrogen, and in which A bonded to ring 1 is asindicated in the structure Ib.

FIG. 1 illustrates by means of a voltammogram the reversible redoxproperties of a film produced from the fluoroindine polymer prepared inExample 1, determined as described in Example 2, and

FIG. 2 illustrates the absorption versus the wavelength of the samefilm.

THE FOLLOWING EXAMPLES ILLUSTRATE THE INVENTION IN GREATER DETAIL.EXAMPLE 1 (METHOD C)

The present Example illustrates the preparation of an electrochromicfluoroindine polymer, poly5,12'-ω-decandiyl-(5,12-dihydro-5,7,12,14-tetraazapentacene)!, by thefollowing reaction: ##STR7##

a) N,N'-bis(2 -nitrophenyl)-1,12-diaminododecane

34 g (0.216 mol) 2-nitro-chlorobenzene and 20 g 1,12-diaminododecane(0.10 mol) are mixed with 40 g potassium carbonate and 200 mlN,N-dimethylformamide (DMF). The mixture is heated with reflux whilesubjected to a vigorous stirring for four hours. Subsequently, theinorganic salts are filtered off and washed with a small amount of DMF.The entire DMF-phase is distilled under vacuum to remove substantiallyall DMF. The remanence is cooled, and 200 ml water are added whilevigorously stirred. Subsequently, the water phase is decanted off, andthe product is caused to crystallize by the addition of approximately100 ml ethanol. The crystals are filtered off, washed twice with 25 mlethanol and 100 ml petroleum ether followed by an air-drying of theproduct. Yield 21.8 g (49%), melting point 79° to 80° C.

b) N,N'-bis(2-aminophenyl)-1,12-diaminododecane

20 g (0.045 mol) N,N'-bis(2-nitrophenyl)-1,12-diaminododecane aredissolved in 100 ml concentrated hydrochloric acid, and 43 g (0.19 mol)stannochloride dihydrate dissolved in 50 ml concentrated hydrochloricacid are added. The mixtured is heated to approxiately 100° C. whilestirred, and after three hours the product separated off is cooled. Thewater phase is separated off, and the product is suspended in 200 ml hotwater, whereafter it is poured into 500 ml 2M sodium hydroxide. Thereleased tetraamine is extracted twice with 150 ml methylchloride, andthe organic phase is dried over magnesium sulphate and evaporated,whereby the product is crystallized. Yield 17.30 g (100%), melting point85° to 88° C.

c) Fluoroindine Polymer: Poly5,12'-omega-decandiyl-(5,12-dihydro-5,7,12,14-tetraazapentacene)!

3.83 g (10 mmol) N,N'-bis(2-aminophenyl)-1,12-diaminododecane isdissolved in 50 ml glacial acetic acid, and 1.68 g (10 mmol)dimethoxyquinone are added. The mixture is heated for reflux under argonfor three hours, whereafter it is evaporated down to dryness. Thedarkblue crystalline mass is treated with 50 ml 10% ammonia solution andwashed thoroughly with water followed by 25 ml acetone. The product isthen thorougly dried under vacuum. Yield 3.90 g (100%).

EXAMPLE 2

0.4 g of the fluoroindine polymer prepared in Example 1 is dissolved in10 ml chloroform and coated by "spincoating" on a glass plate (50 times50 times 1.1 mm) with an indiumtinoxide coating presenting aconductivity of 30 ohm on the surface.

The properties of the electrochromic film is determined by placing saidfilm in an electrochemical cell configuration, in which the glass platerepresents one side of the cell, and where a transparentcounterelectrode of indiumtinoxide on glass and a standard calomelelectrode as reference electrode are used. The cell is filled with 0.5Msulphoric acid, and the electrodes are connected to a potentiostat,whereafter the film is examined by cyclic, electrical voltammetry beinga method of determining the electrochemical properties of electroactivematerials, including their oxidation and reduction potentials.

The resulting cyclic voltammogram appears from FIG. 1 and shows on theX-axis the potential difference between the reference electrode and thefilm, whereas the Y-axis indicates the current at the potential inquestion. The solid line indicates the course when the potential ischanged by 1 mV per second, whereas the dotted line indicates theprogress at 10 mV per scond. During the measuring, the cell is subjectedto an oxidation and reduction cyclus, where the potential is initiallyvaried from +0.25 V to -0.25 V and subsequently back to +0.25 V.

The symmetrical shape of the voltammetric curve indicates that it is aquestion of a reversible reaction, and it appears that the oxidation andthe reduction take place at a potential of approximately -0.1 V relativeto the calomel electrode. This is a fine position within the stabilitywindow of approximately ±1 V relative to the calomel electrode which isdefined by reduction of oxygen and oxidation of water, respectively.

In addition, the spectroscopic properties at various potentials areexamined by the electrochemical cell being placed in aspectrophotometer, and by the optical spectrum being recorded at variouspredetermined potentials. The absorption in absorption units (AU) versusthe wavelength appears from FIG. 2. The solid line is the absorption at+200 mV, the dot-and-dash line at 0 mV, and the dotted line at -400 mV.It appears from the results, that the material reveals heavy absorptionsin the area 550 to 700 nm at a potential of 200 mV relative to thecalomel electrode which corresponds to a strong blue colour unlike thematerial almost not absorbing light in the same area at a potential of-400 mV, in which state the material has a very weak yellow colour(almost colourless).

EXAMPLE 3 (METHOD A)

The present Example illustrates the preparation of a material accordingto the invention by the following reaction course: ##STR8##

a) N-butyl-2-nitroaniline

17.3 g (0.110 mol) 2-chloro-nitrobenzene and 20 ml (14.8 g, 0.29 mol)butylamine are heated to boiling under reflux for four hours. During thecooling, the reaction mixture solidifies into an orange crystal mass,and 50 ml water and 20 ml diluted hydrochloric acid are added. Anextraction is carried out with three times 50 ml CHCl₃. The entireorganic phase is dried over MgSO₄, filtered, and evaporated to an orangeoil. A distillation is performed by oil pump vacuum (approximately 1 mmHg). After an initial fraction at 60° to 125° C., the product isdistilled at 155° to 158° C./1 mm Hg. Yield: 11.24 g (57.9 mmolcorresponding to 52.6%) N-butyl-2-nitroaniline.

b) N-butyl-2-aminoaniline

11.24 g (57.9 mmol) N-butyl-2-nitroaniline in 50 ml concentratedhydrochloric acid are cooled on ice bath to approximately 50° C.,whereafter 50 g (0.22 mol) SnCl₂, H₂ O in 72 ml concentrated HCl areadded. The relatively exothermal process causes the temperature to riseto approximately 70° C. The ice bath is removed when the temperature isapproximately 60° C., and a stirring is performed at this temperaturefor approximately 30 minutes while a slightly pink solution is beingformed.

By cooling on ice bath at a temperature ≧60° C., 85 g NaOH in 100 mlwater are added. Towards the termination of the addition, SnO₂ isprecipitated and is dissolved by further addition. The resulting productis partially precipitated, and the cooled suspension is exctracted twiceby 150 ml ether. The entire organic phase is dried for a short periodover granulated CaCl₂ and evaporated to a clear almost colourless oilwhich crystallizes. Yield: 8.8 g (53.6 mmol, approximately 93%)N-butyl-2-aminoaniline.

c) 5,12-Dibutyl-5,12-dihydro-5,7,12,14-tetraazapentacene

1.65 g (10 mmol) N-butyl-2-aminoaniline and 0.84 g (5 mmol)2,5-dimethoxybenzoquinone i 50 ml glacial acetic acid are heated toboiling under reflux for three hours followed by evaporation to dryness.The darkblue powder is treated with 50 ml 10% ammonia solution andwashed thoroughly with water, ethanol, and acetone (10 ml). After athorough drying under vacuum, 1.95 g (95%)5,12-dibutyl-5,12-dihydro-5,7,12,14-tetraazapentacene is obtained.

EXAMPLE 4

0.2 g 5,12-dibutyl-5,12-dihydro-5,7,12,14-tetraazapentacene is dissolvedin 10 ml chloroform and spincoated on a polyethylene terephthalate filmcoated with indiumtinoxide with a surface resistance of 60 ohm.

The colour-changing properties of the film were determined in anelectrochemical cell configuration with the coated film as one side ofthe cell and a transparent counter-electrode of indiumtinoxide on glassas well as with a standard calomel electrode as reference electrode. Themeasurings were performed in the same manner as in Example 2. The cyclicvoltammogram and the spectrophotometric measurings showed properties ofthe film corresponding to the properties observed of the film examinedin Example 2.

By the reversible process, the colour of the film changes from slightlyyellow in the oxidized form to darkblue in the reduced form.

EXAMPLE 5 (METHOD B) ##STR9## a) 2,3-Diaminophenacine

5 g o-phenylendiamine is dissolved in 150 ml 10% acetic acid and over aperiod of approximately 15 minutes 28 g FeCl₃, 6H₂ O in 50 ml water areadded. The reaction mixture was left for two hours at room temperature.The resulting red crystals are filtered off and washed withapproximately 25 ml water. A suspending is performed in approximately200 ml water, and pH is set to approximately 13 by addition of NaOH,whereafter the resulting yellow product is filtered off and washed withwater and ethanol. The product is suspended in 100 ml boiling ethanol,cooled, and filtered, whereafter a washing is performed with a smallamount of ethanol and petroleum ether. Yield: 2.3 g2,3-diaminophenacine.

b) 2-Carboxy-5,12-dihydro-5,7,12,14-tetraazapentacene

0.5 g 2,3-diaminophenacine and 0.5 g o-diaminobenzoic acid are mixedwith 5 g benzoic acid and heated to 250° C. by means of a heat gun for10 minutes. Upon cooling, the reaction mixture is slowly mixed withboiling ethanol containing a small amount of concentrated HCl to formthe hydrochloride of the dihydrotetraazapentacene at the same time asmost of the benzoic acid is thereby removed. The product is filtered offand washed with additional ethanol and with diluted HCl. Upon drying,other side products are removed by sublimation for a few minutes at 250°C./0.1 mm Hg. The remaining violet-blue powder is pure2-carboxy-5,12-dihydro-5,7,12,14-tetraazapentacene. Yield: 0.2 g.

A coated film produced in the same manner as in Example 4 showscorresponding electrochemical properties. The electrochromic compoundsare, however, sligthly water-soluble and are therefore more suited foruse in non-aqueous structures.

EXAMPLE 6 (METHOD C) Poly5,12'-ω-(3,6-dioxaoctandiyl)-5,12-dihydro-5,7,12,14-tetraazapentacene!##STR10## a) N,N'-bis(2-nitrophenyl)-1,8-diamino-3,6-dioxaoctane

2-nitrochlorobenzene (44 g, 179 mmol) and 19.7 g (133 mmol)1,8-diamino-3,6-dioxaoctane are mixed and heated to approximately 130°C. with the result that an exothermal reaction occurs, where thetemperature of the reaction mixture rises to 190° C. in five minuteswith some development of gas. The reaction flask is removed from the oilbath, and while the reaction mixture solidifies quickly 25 ml xylene areadmixed in order to maintain the possibility of stirring the reactionmixture. When the reaction temperature has dropped to 110° C., thereaction mixture is again heated in oil bath to 170° C. for 90 minutes,whereafter a cooling and addition of 100 ml CH₂ Cl₂ and 100 ml water areperformed. The CH₂ Cl₂ -phase is evaporated into an orange oil which isthen poured into 100 ml water, and by way of seeding a solid masscrystallizes. A filtration is performed, and the filter is washed withapproximately 300 ml water. The moist orange-coloured product isrecrystallized from 300 ml 99% ethanol. Yield: 33.9 g (86,8 mmol, 65,3%)N,N'-bis(2-nitrophenyl)-1,8-diamino-3,6-dioxaoctane.

b) N,N'-bis(2-aminophenyl)-1,8-diamino-3,6-dioxaoctane

26.1 g N,N'-bis(2-nitrophenyl)-1,8-diamino-3,6-dioxaoctane is dissolvedin 100 ml concentrated HCl and stirred while 92.5 g SnCl₂ dissolved in100 ml concentrated HCl are added during approximately two minutes. Thereaction is exothermal and the temperature rises to 90° C. at the sametime as the colour changes from light orange through dark to lightgreen, whereafter a product starts to precipitate. After one hour thereaction mixture is cooled on an ice bath. The crystalline product isfiltered off and dissolved in 150 ml water and added to 50 g NaOH in 300ml ice water. A greenish oil is separated. The product is extracted with100+50 ml CH₂ Cl₂, dried over MgSO₄, and evaporated under vacuum. Yield:21.7 g (57.9 mmol, N,N'-bis(2-aminophenyl)-1,8-diamino-3,6-dioxaoctane.

c) Poly5,12'-ω-(3,6-dioxaoctandiyl)-5,12-dihydro-5,7,12,14-tetraazapentacene!

2.6 g (6.7 mmol) N,N'-bis(2-aminophenyl)-1,8-diamino-3,6-dioxaoctane aredissolved in 50 ml acetic acid, and 1.13 g dimethoxyquinone are added.The mixture is heated to boiling under reflux for three hours, and thereaction mixture turns darkblue. The acetic acid is distilled off, andthe solid product is washed with water and ethanol. The product isthoroughly dried under vacuum. Yield: 2.78 g violet powder of thepolymeric tetraazapentacene stated in the headline. The electrochemicalproperties correspond exactly to the properties of the fluoroindinepolymer produced according to Example 1 as described in Example 2.

EXAMPLE 7 (BATTERY)

0.4 g of the fluoroindine polymer prepared in Example 1 was dissolved in10 ml chloroform and coated on a thin nickel film by an immersingprocess. A solid-state battery is produced from the coated film bycoating the film with a propylene carbonate solution of polyethyleneglycol (20%) and lithium perchlorate (5%). After drying underoxygen-free and steam-free conditions in a glove box, the battery wasclosed by a carbon film impregnated with 10% metallic lithium. Theresulting lihtium-fluoroindine battery operates by the charge beingreleased at a simultaneous reduction of the fluoroindine layer anddissolving of lithium. The process is reversible, and when completelycharged the rechargeable battery provides a potential difference of 2.9V, whereas the potential only drops to approximately 2.5 V in connectionwith a discharging. The battery presents a density of charge of 300Wt/kg in the active layer. By way of comparison the maximum theoreticaldensity of charge of a lead battery is 180 Wt/kg, and in anickel-cadmium battery 200 Wt/kg.

EXAMPLE 8 (LAMINATED ELECTROCHROMIC UNIT)

0.4 g of the fluoroindine polymer produced in Example 1 is dissolved in10 ml chloroform, and 0.2 g polystyrene (molar weight 250,000) is added.This solution is spincoated on a 100 μm thick polyethylene terephthalatefilm (PET) with an indiumtinoxide coating of a specific surfaceresistance of 60 ohm. The film is subsequently reduced under argon byimmersion in a 1M hydrochloric acid solution containing SnCl₂. After ashort rinsing with clean water, the film is spincoated with an aqueoussolution of phosphoric acid (30%) and polyethylene imine (molar weightapproximately 125,000) (9%).

After a complete evaporation of the water content, the coated film iscarefully laminated with PET-film with indiumtinoxide as stated above,here additionally coated with a 3 μm layer of wolframoxide (WO₃). Thecoating is performed by way of cathodic atomization under vacuum (vacuumsputtering). The resulting flexible electrochromic laminate presents inthe resulting form an almost colourless transparency, slightly yellow,and it can be reversibly converted into a strong blue form by applying apotential difference of 0.5 V between the two indiumtinoxide layers.

It is obvious from the above description of the invention that it can bevaried in many ways. Such variations are not to be considered deviationsfrom the scope and idea of the invention, and all such modificationsobvious to persons skilled in the art are also to be consideredcomprised by the following claims.

In the present description and the claims % means % by weight unlessother indications are found.

We claim:
 1. Stable, electroactive material which when a potential isapplied from the outside is subjected to one or more reversible redoxreactions, for use in devices with an electrochromic display or anotherelectrochromic colour change or in batteries, characterised bycontaining at least one condensed ring structure I of one of theformulas I red or I ox in the redox reaction equation: ##STR11## inwhich the groups X, which may be identical or different, are O, S orNR₃, at least one of the groups being NR₃,where the structures A, whichmay be identical or different, may be any molecular structure notblocking the redox reaction, and, optionally, may carry one or moreidentical or different substituents R₄, where R₁, R₂, R₃, and R₄, whichmay be identical or different, may be any substituent not blocking theredox reaction, and where one or more of the substituents R₁, R₂, R₃,and R₄ may also form part of a linker residue L, which is attached toone or more additional ring structures I, and where L is a divalent orpolyvalent group not blocking the redox reaction.
 2. Electrochromicmaterial as claimed in claim 1, characterised by both groups X beingNR₃.
 3. Electroactive material as claimed in claim 1, characterised inthat one or more of the groups R₁, R₂, R₃, and R₄, which may beidentical or different, are a straight or branched chain group with 1 to24 chain atoms selected among C, O, N, S, and Si.
 4. Electroactivematerial as claimed in claim 1 or 2 or 3, characterised in that one ormore of the groups R₁, R₂, R₃, and R₄, which may be identical ordifferent, are alkyl with 1 to 18 carbon atoms, thioalkyl with 1 to 18carbon atoms, and 1 to 6 sulphur atoms, oxoalkyl with 1 to 18 carbonatoms, and 1 to 6 oxygen atoms, nitro, halogen, phenyl, alkenyl with 1to 18 carbon atoms, cyano, hydroxy, alkoxy with 1 to 6 carbon atoms oralkylamino with 1 to 6 carbon atoms.
 5. Electroactive material asclaimed in claim 1, characterised in that one or both structures Acomprise a carbocyclic or heterocyclic ring condensed with ring No. 1and/or ring No. 3, respectively, in the structure I.
 6. Electroactivematerial as claimed in claim 5, characterised in that the carbocyclic orheterocyclic ring is aromatic.
 7. Electroactive material as claimed inclaim 1, characterised in that it is an oligomeric or polymericmaterial, in which the ring structure I forms part, where the polymericstructure results from linker residues L.
 8. Electroactive material asclaimed in claim 7, characterised in that the linker residues L arestraight chained or branched, divalent or polyvalent groups with 3 to150 chain atoms selected among C, O, N, S, and Si.
 9. Electroactivematerial as claimed in claim 7 or 8, characterised in that the linkerresidues are derived from one or more precursor materials (monomer orprepolymer) selected among precursor materials to polyalkene, polyether,polysulphide, polyamine, silicone or mixtures thereof.
 10. A method forthe preparation of a stable electroactive material in form of a compoundcontaining a condensed ring structure I of the formula shown in claim 1,in which the groups X, which may be identical or different, are O, S orNR₃, and where A, R₁, R₂, R₃, and R₄ may have any meaning indicated inclaim 1, with the proviso that none of the substituents R₁, R₂, R₃, andR₄ can form part of a linker residue L attached to additional ringstructures characterised bya) reacting an amine of the formula II##STR12## where A and X have the meanings stated above, with a quinoneof the formula III ##STR13## where R₁ and R₂ have the meanings statedabove, and Q₁ is hydrogen or C₁₋₄ alkyl, or b) for the preparation ofcompounds of the ring structure Ib, in which Ib ox has the formula##STR14## in which R₃ and A have the meanings stated above, where R_(a)and R_(b) may have the same meaning as the groups R₁, R₃, and R₄, andwhere each of the two groups R_(a/b) is the same as R_(a) and R_(b),respectively, reacting 2 molecules of an o-phenylene diamine of theformula IV ##STR15## in which R_(a) and R_(b) have the meanings statedabove, in the presence of an oxidation agent to form a compound of theformula V ##STR16## in which R_(a), R_(b), and R_(a/b) have the meaningsstated above, and then reacting the compound of the formula V with acompound of the formula VI ##STR17## in which R₃ and A have the meaningsstated above.
 11. A method for the preparation of a stable electroactivematerial as claimed in claim 1 in form of an oligomeric or polymericmaterial containing several ring structures I, in which X, A, R₁, R₂,R₃, and R₄ have the meanings stated in claim 1, and in which one or morelinker residues L having the meaning sated in claim 1 form part,characterised byc) for the preparation of an electroactive polymericmaterial of the following structure ##STR18## in which A, R₁, R₂, and Lhave the meanings stated above, and n is the polymerisation degree,reacting a compound of the formula VII ##STR19## in wich A has themeaning stated in claim 1, and Q₂ is a leaving group, with a diaminecompound of the formula

    H.sub.2 N-L-NH.sub.2                                       VIII

where L has the meaning stated in claim 1, to form a compound of theformula IX ##STR20## where A and L have the meaning stated above,reducing the compound of the formula IX to obtain a compound of theformula X ##STR21## in which A and L have the meanings stated above, andreacting the compound of formula X with a quinone of the formula III##STR22## in which R₁ and R₂ have the meanings stated above, and Q₁ ishydrogen or C₁₋₄ alkyl, or d) for the preparation of a polymeric,electroactive material with the structure Id, where Id ox has thestructure ##STR23## in which R₁, R₂, R₃, and L have the meanings statedabove, n is the polymerization degree and A₁ is a structure A comprisinga benzene ring, reacting a compound of the formula XI ##STR24## in whichA₁ has the meaning stated above, and Q₃ is a protecting group, with adiamine compound of the formula VIII

    H.sub.2 N-L-NH.sub.2                                       VIII

in which L has the meaning stated above, to obtain a compound of theformula XII ##STR25## in which A₁, L, and Q₃ have the meanings statedabove, nitrating the rings A₁ in the o-position into the groups NHQ₃ inthe compound of the formula XII, and in arbitrary sequence orsimultaneously reducing the nitro groups and removing the protectinggroups Q₃ to form a compound of the formula XIII ##STR26## in which A₁and L have the meanings stated above, and reacting the compound of theformula XIII with a compound of the formula III ##STR27## in which R₁,R₂, and Q₁ have the meanings stated above, to form a polymeric compoundwith the structure Id, in which R₃ is hydrogen and, optionally, astermination or at a suitable stage during the synthesis converting oneor more hydrogen groups R₃ into R₃ -groups having another of themeanings stated for R₃, or e) for the preparation of a polymericstructure Ie, in which Ie ox is of the formula ##STR28## in which A, R1,L and n have the meanings stated above reacting a compound of theformula XIV ##STR29## in which A, R₁, and R₂ have the meanings stated inclaim 1, with a compound of the formula XV

    Q.sub.4 -L-Q.sub.4                                         XV

in which Q₄ is a leaving group.